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  • Added sugar, and processed fructose in particular, is a primary driver of the metabolic dysfunction underlying obesity, diabetes, and heart disease
  • To prevent chronic disease such as diabetes, heart disease, and cancer, WHO suggests limiting your added sugar consumption to a maximum of five percent of your daily calories
  • Studies have shown that those who consume 25 percent or more of their daily calories as sugar are twice as likely to die from heart disease as those who get less than 7-10 percent of their calories from sugar

Elevated Sugar Intake Linked to Significantly Raised Risk of Obesity, Diabetes, and Heart Disease

March 16, 2015 | 263,961 views
| Available in EspañolDisponible en Español

By Dr. Mercola

According to a study published in 2013, nearly one in five US deaths is now associated with obesity. Obesity is indeed a marker for chronic and potentially deadly disease, but the underlying problem that links obesity to so many other serious health issues—including heart disease—is metabolic dysfunction.

Mounting evidence clearly shows that added sugars, and processed fructose in particular, is a primary driver of metabolic dysfunction.

Refined fructose is actually broken down very much like alcohol, damaging your liver and causing mitochondrial and metabolic dysfunction in the same way as ethanol and other toxins.

It also causes more severe metabolic dysfunction because it’s more readily metabolized into fat than any other sugar. The fact that refined fructose is far more harmful to your health than other sugars was recently highlighted in a meta-review published in the Mayo Clinic Proceedings.1

The average American consumes one-third of a pound of sugar per day, half of which is processed fructose. Other statistics found in Dr. Richard Johnson’s book, The Sugar Fix,2 suggest about 50 percent of Americans consume as much as half a pound, more than 225 grams, per day!

The majority of all this sugar is hidden in processed foods and beverages, so to address obesity and related health issues like diabetes and heart disease, ridding your diet of processed fare is key for success.

WHO Urges Slashing Sugar Consumption to Protect Health

To lower your risk of obesity and tooth decay, the World Health Organization (WHO) recommends dramatically reducing your sugar consumption, limiting added sugar to 10 percent of daily calories or less.3 This equates to about 12 teaspoons or 50 grams of sugar for most adults.

To prevent chronic disease such as diabetes, heart disease, and cancer, the organization suggests limiting your sugar consumption to a maximum of five percent of your daily calories.

The latter five percent limit is right in line with my own standard recommendation for healthy people, which calls for keeping your total fructose consumption below 25 grams per day, or about five teaspoons.

However, if you already have signs of insulin resistance, such as hypertension, obesity, or heart disease, I believe you’d be wise to limit your total fructose consumption even further—down to 15 grams or less until your weight and other health conditions have normalized.

Three recent studies that have linked excessive sugar consumption to chronic disease include the following:

  • According to the meta-review4 mentioned earlier, the preponderance of research clearly shows that once you reach 18 percent of your daily calories from added sugar, there’s a two-fold increase in metabolic harm that promotes prediabetes and diabetes
  • Most recently, a study published in the Journal of the American Medical Association (JAMA)5 concluded that “most US adults consume more added sugar than is recommended for a healthy diet,” and that there’s “a significant relationship between added sugar consumption and increased risk for cardiovascular disease mortality.”
  • The 15-year long study, which included data for 31,000 Americans, found that those who consumed 25 percent or more of their daily calories as sugar were more than twice as likely to die from heart disease as those who got less than 10 percent of their calories from sugar.

    On the whole, the odds of dying from heart disease rose in tandem with the percentage of added sugar in the diet regardless of the age, sex, physical activity level, and body-mass index.

  • A 2014 study6 came to very similar results. Here, those who consumed the most sugar — about 25 percent of their daily calories — were twice as likely to die from heart disease as those who limited their sugar intake to seven percent of their total calories.

Fried Foods Also Linked to Increased Risk for Heart Disease

Added sugar isn’t the only disease-promoting factor in your diet though. Harmful fat found in fried foods is another important one.

Preliminary research7 findings presented at a recent American Heart Association meeting linked fried food consumption with an increased risk for heart failure. Data on more than 15,300 male doctors participating in the Physicians' Health Study was collected and analyzed. The average follow-up period was 10 years.

  • Those who reported eating fried food up to three times per week had an average of 18 percent increased risk of developing heart failure
  • Eating fried food four to six times a week was associated with a 25 percent increased risk, and
  • Eating fried foods seven times per week or more was associated with a 68 percent greater risk for heart failure

According to lead researcher Dr. Luc Djousse, associate professor of medicine at Harvard Medical School:

"This study suggests that it might be wise to reduce the frequency and quantity of fried foods consumed weekly in order to prevent heart failure and other chronic conditions.”

Why Fried Foods Promote Heart Disease

These kinds of findings are not all that surprising. Dr. Fred Kummerow, author of Cholesterol Is Not the Culprit, was the first researcher to discover that consumption of trans fat—but not saturated fat—led to clogged arteries. He published the first article on this association in 1957.

Some of his most recent research8 shows that there are two types of fats in our diet responsible for the formation of heart disease:

  1. Trans fat found in partially hydrogenated oil. Structurally, trans fats are synthetic fatty acids. Fourteen of them are produced during the hydrogenation process. (They are not present in either animal or vegetable fats.) 
  2. Trans fats prevent the synthesis of prostacyclin,9 which is necessary to keep your blood flowing. When your arteries cannot produce prostacyclin, blood clots form, and you may succumb to sudden death.

    Mounting research suggests there is NO safe limit for trans fat. This makes it an even greater concern than sugar, which your body can safely handle in small doses. Trans fat also increases insulin resistance.

  3. Oxidized cholesterol, formed when polyunsaturated vegetable oils (such as soybean, corn, and sunflower oils) are heated. A primary source is fried foods. This oxidized cholesterol (not dietary cholesterol in and of itself) causes increased thromboxane formation—a factor that clots your blood.  As noted by Dr. Kummerow in a previous New York Times interview:10
  4.  “The problem is not LDL, the ‘bad cholesterol’ widely considered to be the major cause of heart disease. What matters is whether the cholesterol and fat residing in those LDL particles have been oxidized... “ Cholesterol has nothing to do with heart disease, except if it’s oxidized”...

    [T]he high temperatures used in commercial frying cause inherently unstable polyunsaturated oils to oxidize, and that these oxidized fatty acids become a destructive part of LDL particles. Even when not oxidized by frying, soybean and corn oils can oxidize inside the body.”
    [Emphasis mine]

Heart-Healthy Basics

Two diet modifications that are foundational for successful weight management and disease-prevention are a) limiting your processed food consumption, and b) increasing the amount of healthy fat and fresh whole foods in your diet.

Avoiding processed foods will automatically reduce your added sugar consumption and your exposure to harmful fats, which again include both trans fats and oxidized cholesterol. Grains, including whole grains, are also best avoided if you’re insulin/leptin resistant, have diabetes, high blood pressure, heart disease, or are overweight, as grains and other sugar-forming starchy carbohydrates lead to adverse insulin reactions.

Remember, just like fructose, trans fats interfere with your insulin receptors, thereby increasing your risk for diabetes11 and related health problems. Healthy saturated fats do not do this. For optimal health, most people may actually need upwards of 50-85 percent of their daily calories in the form of healthy fats; good sources of which include coconut and coconut oil, avocados, butter, animal fats, and raw nuts.

Tree Nuts Are a Healthy Addition to Your Diet

A number of studies have confirmed that tree nuts can help prevent chronic disease, including metabolic syndrome, type 2 diabetes, and heart disease. The fat content of nuts—along with naturally-occurring antioxidants—may have a great deal to do with this. For example, one large-scale, 30-year long Harvard study12 found that people who ate a small handful of nuts at least seven times per week were 20 percent less likely to die for any reason, compared to those who largely avoided nuts. They were also leaner than their nut-eschewing counterparts.

Another study13 published in the Annals of Internal Medicine found that middle-aged women who followed a Mediterranean-style diet rich in nuts and vegetables were approximately 40 percent more likely to survive into later decades without developing some form of chronic disease. All nuts are not necessarily created equal however, and tree nuts are, from a nutritional stand point, far preferable to peanuts, which is technically a legume.

My main objections to peanuts are that they tend to distort your omega 3 to omega 6 ratio as they are relatively high in omega 6; they’re also frequently contaminated with a carcinogenic mold called aflatoxin and, perhaps surprisingly, peanuts tend to be heavily sprayed with pesticides. Most nuts’ nutritional makeup  closely resemble what I consider to be an ideal ratio of the basic building blocks—fat making up the greatest amount of your daily calories, followed by a moderate amount of high quality protein and a low amount of non-vegetable carbs.

My favorite nuts are raw organic macadamia and pecans, as they provide the highest amount of healthy fat while being on the lower end in terms of carbs and protein. The main fatty acid in macadamia nuts is the monounsaturated fat oleic acid (about 60 percent). This is about the level found in olives, which are also well known for their health benefits. Macadamia nuts also contain high amounts of vitamin B1, magnesium, and manganese.

Pecans contain more than 19 vitamins and minerals, and research has shown they may help lower LDL cholesterol and promote healthy arteries. In the Harvard study,14 those who ate a one-ounce serving seven times or more per week appeared to benefit the most. One ounce of nuts equates to just over 28 grams, or about a small handful. The following list shows the nutrition facts15  in grams per one ounce for your most common tree nuts:

Tree Nut
Numbers are grams per ounce
Fat Protein Carbohydrates
Macadamias 22 2 4
Pecans 20 3 4
Pine nuts 20 4 4
Brazil nuts 19 4 3
Walnuts 18 4 4
Hazelnuts 17 3 5
Cashews 13 4 9
Almonds 14 6 6
Pistachios 13 6 8

Obesity, Diabetes, and Heart Disease Are All Preventable

Nearly one in five US deaths is associated with obesity, and one in every three deaths is attributed to cardiovascular disease, which includes heart attacks and stroke. According to a 2013 report16 from the US Center for Disease Control and Prevention (CDC), of the 800,000 cardiovascular disease deaths occurring in the US each year, a quarter of them —or about 200,000—could be prevented through simple lifestyle changes. Personally, I believe the rate of prevention could be far higher than that—especially if great attention was paid to sugar consumption. According to statistics found in the Credit Suisse Research Institute’s 2013 study17 Sugar Consumption at a Crossroads, up to 40 percent of US healthcare expenditures are for diseases directly related to the overconsumption of sugar.

We actually spend more than a trillion dollars each year fighting the damaging health effects of sugar!  To protect your health, please consider restricting your fructose consumption to 25 grams per day or less. If you're overweight or have a disease such as cancer, diabetes, or heart disease (or are at high risk for them) then you're probably better off further reducing your fructose intake to 15 grams per day or less (and this includes all sources—HFCS, sugar, honey, agave, fruit, fruit juice, maple syrup, etc.)

Doing this will help you normalize your insulin- and leptin levels, thereby reducing your risk of not only diabetes and heart disease, but also a long list of other chronic health problems. Key to success when cutting out added sugar is to replace the lost calories (energy) with high-quality healthy fat, which includes avocados; butter made from raw grass-fed organic milk; raw dairy; organic pastured egg yolks; coconuts and coconut oil; unheated organic nut oils; raw nuts and seeds; and grass-fed and finished meats. For even more heart-healthy lifestyle tips, please see my dedicated heart disease page.

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